The next-generation multimedia wireless communication system, on which research is actively ongoing, is requested to process various information such as image data, radio data, and the like, beyond the early voice-oriented services, at a high data transmission rate.
Recently, orthogonal frequency division multiplexing (OFDM) supporting a high data transmission rate receives much attention. The OFDM is a multi-carrier modulation scheme in which a frequency band is divided into a plurality of orthogonal subcarriers to transmit data. Orthogonal frequency division multiple access (OFDMA) is a scheme providing multiplexing of multiple users by combining frequency division multiple access (FDMA), time division multiple access (TDMA), or code division multiple access (CDMA) to the OFDM.
A wireless communication system includes a base station (BS) and one or more mobile stations (MSs). MSs may be fixed or mobile, and may be referred to by other names such as user equipment (UE), user terminal (UT), subscriber station (SS), wireless device, etc. The BS generally refers to a fixed station that communicates with the MSs and may be called by other names such as node B, base transceiver system (BTS), access point (AP), etc. In the following description, uplink (UL) refers to transmission from the MSs to the BS, and downlink (DL) refers to transmission from the BS to the MSs.
The wireless communication system has a cell structure to configure an effective system. Cells refer to zones formed as a large area is divided in order to effectively use frequency. In general, a BS is installed in a central portion of a cell to relay MSs, and the cell refers to a service area provided by the single BS.
When neighboring cells in the OFDM/OFDMA system in a multi-cell environment use the same subcarrier, it potentially causes interference between users. This is called an inter-cell interference. In particular, the inter-cell interference is much problematic to an MS located near a cell boundary. In downlink, an MS located near the cell boundary is strongly affected by a neighboring cell. In uplink, an MS located near the cell boundary strongly affects a neighboring cell and has a low transmission rate due to a path loss in its serving cell.
In order to reduce the inter-cell interference, neighboring cells may use different sub-carriers, which, however, causes a problem in that radio resources used by the single BS are reduced.
Thus, in order to reduce the inter-cell interference in the multi-cell environment, a multi-cell cooperative method has been proposed. The use of the multi-cell cooperative method can improve a communication performance of the MS located near the cell boundary. In line with this, an effective scheduling method of a BS using the multi-cell cooperative method is required.